The present invention relates to a sealing structure of a wheel supporting device for preventing intrusion of muddy water or the like into a rolling bearing in the wheel supporting device.
Generally, the wheel supporting device which supports a wheel at a driven side of an automobile or the like includes an axle mounted on a vehicle body, and a housing in an annular shape to which the wheel is attached and which is rotatably held around the axle interposing a rolling bearing. In the wheel supporting device of this type, a sealing structure is provided for the purpose of preventing intrusion of strange obstacles such as muddy water, gravels, pebbles, into the rolling bearing, and breakdown of the rolling bearing. As an example of this sealing structure, such a structure that a seal member such as a pack seal is disposed in an annular clearance between an outer peripheral surface of the axle and an inner peripheral surface of the housing, outside the rolling bearing in an axial direction, as disclosed in JP-A-2003-21151, has been widely known.
FIG. 9 is a longitudinal sectional view showing the sealing structure of the wheel supporting device as disclosed in JP-A-2003-21151. As shown in FIG. 9A, this wheel supporting device includes an axle 100 which is mounted on a vehicle body, a housing 110 to which a wheel is attached, and a rolling bearing 120 which supports the housing 110 so as to rotate with respect to the axle 100. A pair of inner rings 121 which are components of the rolling bearing 120 are fitted over an outer periphery of the axle 100. The inner rings 121 are clamped between a nut 101 which is screwed from an end part of the axle 100 and a shoulder part 102 which is formed at a base end of the axle 100, thereby to be fixed to the axle 100. An outer ring 122 which is a component of the rolling bearing 120 is fitted into a center bore 111 of the housing 110. The outer ring 122 is clamped between a rib part 112 which is formed in the center bore 111 and a snap ring 113 which is fitted into the center bore 111, thereby to be fixed to the housing 110. Moreover, the housing 110 is provided with a flange part 114 to which the wheel is adapted to be fit. The rolling bearing 120 is a double row angular ball bearing, and includes balls 123 which are arranged in double rows between a raceway surface formed on outer peripheral surfaces of the inner rings 121 and a raceway surface formed on an inner peripheral surface of the outer ring 122.
In addition, a pack seal 130 is provided in an annular clearance between the outer peripheral surface of the axle 100 and the inner peripheral surface of the housing 110, at an inner side of the rolling bearing 120 (an opposite side to the side where the wheel is attached), so that intrusion of muddy water or the like from the exterior may be prevented. As shown in FIG. 9B, the pack seal 130 includes a slinger 131 which is fitted to the outer peripheries of the inner rings 121, and a seal member 132 which is fitted to an inner periphery of the center bore 111 of the housing 110. The slinger 131 is formed in an L-shape in cross section having a cylindrical part 131a, and a flange part 131b which extends radially outward from this cylindrical part 131a. The seal member 132 has radial lips 132a and 132b in a bifurcated shape which are in sliding contact with the cylindrical part 131a of the slinger 131, and a side lip 132c which is in sliding contact with the flange part 131b of the slinger 131. The seal member 132 is formed by bonding the radial lips 132a, 132b and the side lip 132c integrally to a core wire 133 by vulcanized boding of rubber. In this manner, by providing the pack seal 130 at the inner side of the rolling bearing 120, the sealing structure is formed so that intrusion of muddy water or the like from the exterior may be prevented, and damage of the rolling bearing by the intrusion of the muddy water or the like may be restrained.
By the way, in the wheel supporting device as disclosed in No. JP-A-2003-21151, it is sometimes difficult to reliably prevent intrusion of the muddy water or the like into the rolling bearing, because the sealing structure at the inner side of the rolling bearing depends only on the pack seal. Specifically, because there is no other sealing structure in a region from the exterior of the vehicle to the pack seal, it would be probable that a large amount of muddy water or the like may be delivered to the pack seal. In case where a large amount of the muddy water or the like has been delivered, it becomes difficult to reliably exclude the muddy water or the like only by sealing function of the pack seal, and there is such anxiety that a large amount of the muddy water or the like may intrude into the rolling bearing.